A memory card is widely used as a data storage medium for a digital camera, etc. In such a memory card, a flash memory, which is a nonvolatile semiconductor memory, is often embedded. Also, a controller chip is embedded in the memory card, which controls to input and output from/to the flash memory.
FIG. 1 shows a configuration diagram of a conventional memory card. A memory card 101 is connected to an external device 104 such as a digital camera through external terminals 100. In memory card 101, there are embedded a memory chip 103 having a memory core 110 and an input/output buffer 109, and a controller chip 102 which controls write operation, read operation, erase operation, etc.
Memory chip 103 is provided with a number of connection terminals 107 including command terminal, address terminal, data input/output terminal, and power terminal, through which memory chip 103 is connected to controller chip 102. Meanwhile, in order to eliminate data inversion errors caused by noise, the number of external terminals 100 mounted on memory card 101 has to be reduced. For this purpose, controller chip 102 stores a write data and an address transferred from external device 104 into buffer 105 once, and then transfers these data and address to memory chip 103 together with a control command sent from external device 104.
Controller chip 102 has a card interface 111, a buffer 105, a transfer circuit 106 which transfers data to/from memory chip 103, and a buffer controller 108 which controls buffer 105. Further, controller chip 102 has a buffer status register 112 which indicates whether effective data and address is stored in buffer 105.
An exemplary write operation in the conventional memory card is described in the following. Through external terminals 100, both a data transfer command and a transfer data are serially input, and the transfer data is stored into buffer 105. This operation is hereinafter referred to as ‘external transfer’. Thereafter, an address transfer command and a transfer address are serially input, and the transfer address is also stored into buffer 105. When such effective data are stored into buffer 105, buffer controller 108 sets ‘1’ into a flag in buffer status register 112. Thereafter, when a memory access command and a write command indicating a detail of access are serially input, buffer controller 108 confirms the effective flag in buffer status register is ‘1’, and then transfers the transfer data and the transfer address stored in buffer 105 to input/output buffer 109 in memory chip 103 through transfer circuit 106. This operation is hereinafter referred to as ‘internal transfer’. At this time, the write command is also transferred to memory chip 103. As a result, data write operation into memory core 110 is completed. On completion of the internal transfer, buffer controller 108 resets the flag in buffer status register 112 to ‘0’. This causes to clear the data having been stored in buffer 105.
Now, in a shipping test process of a memory card, predetermined data are written into the memory card, and whether or not the data are correctly read out is examined. In the aforementioned shipping test, it is required to write data which are apt to induce errors when any defect is contained in the memory card. For example, in order to enable the detection of a short-circuit defect between adjacent bit lines, a data having a reverse pattern is written into an adjacent cell. Or, in other cases, data having a checkered pattern, that is, a reverse data in vertical and horizontal directions, are written into four cells located in mutually adjacent positions.
However, as mentioned earlier, there are provided a small number of terminals 100 in the memory card. Therefore, it requires substantially a long time to write test data through such external terminals having a narrow bus width. Particularly, in recent years, a flash memory becomes highly integrated and has a larger capacity than before. Accordingly, capacity of the memory card tends to increase. This necessitates increased processing steps and time for writing test data, resulting in bringing about increased cost in manufacturing such a memory card.